[llvm-dev] Using C++14 code in LLVM

[Zachary Turner via llvm-dev]

On Sat, Oct 1, 2016 at 11:46 PM Joerg Sonnenberger via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> On Sun, Oct 02, 2016 at 05:33:40AM +0000, Zachary Turner via llvm-dev
> wrote:
> > While GCC doesn't claim to "fully" support C++14 until 5.2 (which is only
> > about 1 year old), you can get all of the above features with GCC 4.9
>
> I do care quite a bit about GCC 4.8 support, since that's what is
> shipped with NetBSD 7.
>
> > One potentially added benefit of this is that GCC supports <regex> in
> 4.9.
> > This might allow us to kill of llvm::Regex in favor of standardizing on
> > std::regex, as GCC is currently the only supported compiler without a
> regex
> > implementation.
>
> If that is the only argument, we should be able to reuse the libc++
> implementation without too much trouble?
>

That wasn't even the main argument :)  The main argument was the ability to
use C++14 in the upstream.  I suspect that we won't want to be tied to
C++11 indefinitely though.  LLVM already has a section called "Getting a
modern host C++ toolchain" for distros with older GCC's.  In theory this
could just be bumped from "older than GCC 4.7" to "older than GCC 4.9".  I
admit I don't know much (i.e. anything) about NetBSD.  But a quick look at
the release history says that even NetBSD 8 (which isn't even stable yet),
is still only going to have GCC 4.8.  So if we're going to be held back by
this, we're looking at 2-4 years before we can use C++14 upstream.  Just
food for thought.

That said, will the libc++ implementation work with MSVC?  I don't know,
but I seriously doubt it.
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